Ondansetron is a serotonin 5-HT3 receptor antagonist with the following structure:

Ondansetron's primary use is as an antiemetic (to treat nausea and vomiting) following cancer treatments such as chemotherapy, surgery and/or radiation. Ondansetron works by reducing the activity of the vagus nerve which then deactivates the vomiting center in the medulla oblongata. Ondansetron also blocks serotonin receptors in the chemoreceptor trigger zone.
Ondansetron is currently available from GlaxoSmithKline as a film coated tablet, an oral solution, as an injection (Zofran®), and an orally disintegrating tablet (Zofran ODT®). Ondansetron is also available as an oral soluble film (Zuplenz®) from Vestiq Pharmaceuticals.
U.S. Pat. No. 6,998,110 discloses a method for administering a composition, such as ondansetron, to a mammal through the oral mucosa. This patent teaches that a polar solvent and a propellant are required. Although U.S. Pat. No. 6,676,931 teaches a propellant free ondansetron composition, this patent requires the use of a pharmacologically acceptable polar solvent in an amount of 19 to 90 weight percent and flavoring agent in an amount of 0.1 to 10 weight percent of the total composition.
U.S. Pat. No. 5,854,270 is directed to a liquid ondansetron formulation that includes a sorbitol-containing sweetener and has a pH of from 2 to 5. U.S. Pat. No. 6,555,546 discloses a formulation which may contain ondansetron and polyethylene glycol (PEG)-electrolyte solution for use in treating constipation or for accelerating intestinal lavage. However, these formulations fail to provide a sublingual formulation that has quick-onset and is storage stable.
“Sublingual” means “under the tongue” and refers to administration of a substance via the mouth in such a way that the substance is rapidly absorbed via the blood vessels under the tongue. A sublingual formulation is desirable because it bypasses hepatic first pass metabolic processes which provide better bioavailability, rapid onset of action, and higher patient compliance. Dysphagia (difficulty in swallowing) is common among in all ages of people and more in pediatric, geriatric, and psychiatric patients. In terms of permeability, the sublingual area of oral cavity is more permeable than buccal area. Sublingual drug administration is applied in field of cardiovascular drugs, steroids, enzymes and barbiturates.
While there are various ondansetron formulations currently available, there is still a need in the art for a rapid onset, storage stable, sublingual spray formulation containing ondansetron, or a pharmaceutically acceptable salt thereof.